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Diffstat (limited to 'absl/strings/internal/pow10_helper_test.cc')
| -rw-r--r-- | absl/strings/internal/pow10_helper_test.cc | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/absl/strings/internal/pow10_helper_test.cc b/absl/strings/internal/pow10_helper_test.cc new file mode 100644 index 000000000000..9a13d5240da7 --- /dev/null +++ b/absl/strings/internal/pow10_helper_test.cc @@ -0,0 +1,120 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/strings/internal/pow10_helper.h" + +#include <cmath> + +#include "gtest/gtest.h" +#include "absl/strings/str_format.h" + +namespace absl { +namespace strings_internal { + +namespace { + +struct TestCase { + int power; // Testing Pow10(power) + uint64_t significand; // Raw bits of the expected value + int radix; // significand is adjusted by 2^radix +}; + +TEST(Pow10HelperTest, Works) { + // The logic in pow10_helper.cc is so simple that theoretically we don't even + // need a test. However, we're paranoid and believe that there may be + // compilers that don't round floating-point literals correctly, even though + // it is specified by the standard. We check various edge cases, just to be + // sure. + constexpr TestCase kTestCases[] = { + // Subnormals + {-323, 0x2, -1074}, + {-322, 0x14, -1074}, + {-321, 0xca, -1074}, + {-320, 0x7e8, -1074}, + {-319, 0x4f10, -1074}, + {-318, 0x316a2, -1074}, + {-317, 0x1ee257, -1074}, + {-316, 0x134d761, -1074}, + {-315, 0xc1069cd, -1074}, + {-314, 0x78a42205, -1074}, + {-313, 0x4b6695433, -1074}, + {-312, 0x2f201d49fb, -1074}, + {-311, 0x1d74124e3d1, -1074}, + {-310, 0x12688b70e62b, -1074}, + {-309, 0xb8157268fdaf, -1074}, + {-308, 0x730d67819e8d2, -1074}, + // Values that are very close to rounding the other way. + // Comment shows difference of significand from the true value. + {-307, 0x11fa182c40c60d, -1072}, // -.4588 + {-290, 0x18f2b061aea072, -1016}, // .4854 + {-276, 0x11BA03F5B21000, -969}, // .4709 + {-259, 0x1899C2F6732210, -913}, // .4830 + {-252, 0x1D53844EE47DD1, -890}, // -.4743 + {-227, 0x1E5297287C2F45, -807}, // -.4708 + {-198, 0x1322E220A5B17E, -710}, // -.4714 + {-195, 0x12B010D3E1CF56, -700}, // .4928 + {-192, 0x123FF06EEA847A, -690}, // .4968 + {-163, 0x1708D0F84D3DE7, -594}, // -.4977 + {-145, 0x13FAAC3E3FA1F3, -534}, // -.4785 + {-111, 0x133D4032C2C7F5, -421}, // .4774 + {-106, 0x1D5B561574765B, -405}, // -.4869 + {-104, 0x16EF5B40C2FC77, -398}, // -.4741 + {-88, 0x197683DF2F268D, -345}, // -.4738 + {-86, 0x13E497065CD61F, -338}, // .4736 + {-76, 0x17288E1271F513, -305}, // -.4761 + {-63, 0x1A53FC9631D10D, -262}, // .4929 + {-30, 0x14484BFEEBC2A0, -152}, // .4758 + {-21, 0x12E3B40A0E9B4F, -122}, // -.4916 + {-5, 0x14F8B588E368F1, -69}, // .4829 + {23, 0x152D02C7E14AF6, 24}, // -.5000 (exactly, round-to-even) + {29, 0x1431E0FAE6D721, 44}, // -.4870 + {34, 0x1ED09BEAD87C03, 60}, // -.4721 + {70, 0x172EBAD6DDC73D, 180}, // .4733 + {105, 0x1BE7ABD3781ECA, 296}, // -.4850 + {126, 0x17A2ECC414A03F, 366}, // -.4999 + {130, 0x1CDA62055B2D9E, 379}, // .4855 + {165, 0x115D847AD00087, 496}, // -.4913 + {172, 0x14B378469B6732, 519}, // .4818 + {187, 0x1262DFEEBBB0F9, 569}, // -.4805 + {210, 0x18557F31326BBB, 645}, // -.4992 + {212, 0x1302CB5E6F642A, 652}, // -.4838 + {215, 0x1290BA9A38C7D1, 662}, // -.4881 + {236, 0x1F736F9B3494E9, 731}, // .4707 + {244, 0x176EC98994F489, 758}, // .4924 + {250, 0x1658E3AB795204, 778}, // -.4963 + {252, 0x117571DDF6C814, 785}, // .4873 + {254, 0x1B4781EAD1989E, 791}, // -.4887 + {260, 0x1A03FDE214CAF1, 811}, // .4784 + {284, 0x1585041B2C477F, 891}, // .4798 + {304, 0x1D2A1BE4048F90, 957}, // -.4987 + // Out-of-range values + {-324, 0x0, 0}, + {-325, 0x0, 0}, + {-326, 0x0, 0}, + {309, 1, 2000}, + {310, 1, 2000}, + {311, 1, 2000}, + }; + for (const TestCase& test_case : kTestCases) { + EXPECT_EQ(Pow10(test_case.power), + std::ldexp(test_case.significand, test_case.radix)) + << absl::StrFormat("Failure for Pow10(%d): %a vs %a", test_case.power, + Pow10(test_case.power), + std::ldexp(test_case.significand, test_case.radix)); + } +} + +} // namespace +} // namespace strings_internal +} // namespace absl |